The goal of this project is to provide insight into the "mucous secretory defect" in cystic fibrosis (CF) by providing baseline information on intestinal mucus secretion from normal goblet cells. Although CF intestinal mucus may be abnormally viscous, no specific abnormality has been identified in CF tissue to account for this altered physiochemical behavior. The present study will approach the problem from several different aspects. First, studies will be continued to identify the agents which accelerate or inhibit normal secretory rates in the intestine. This will be monitored by autoradiography and by a sensitive enzymeimmunoassay (EIA) for rat intestinal mucus. Secondly, the intracellular transport of granules will be monitored by autoradiography during a variety of experimental secretory states, including: 1) baseline secretion; 2) accelerated secretion; 3) recovery from accelerated secretion; and 4) chronic accelerated secretion. The mechanisms by which granules are segregated and transported will be investigated through a comprehensive analysis of the goblet cell cytoskeleton in each of the above secretory states using ultrastructural, freeze fracture and immunocytochemical techniques. Membrane alterations during experimental secretory states will also be monitored by ultrastructural and freeze fracture methodologies. Finally, a chronic hypersecretory state will be experimentally induced using either cholinergic agents or luminal irritants. Alterations in granule movement patterns will be monitored by autoradiography and alterations in intestinal cell populations will be determined. The ultimate goal of this project is to identify the normal responses of intestinal goblet cells to experimental secretory conditions. Only then can meaningful experiments utilizing normal human and CF tissue be planned, and abnormalities in the secretory process in CF tissue be determined.